The present invention relates to torque sensors, specifically to torque sensors using non-contact optics for the measurement of torque, torque angle, flexure speed, flexure direction and flexure rotational travel.
A conventional method and device for measuring torque generally requires physical contact with the torque sensor's center shaft. Applying torque to a shaft generates two principal lines of stress along helical lines which are orthogonal to each other on the surface of the shaft. Strain gauges are bonded in a cross arrangement along the helical lines. The strain gauges are coupled to measuring electronics by slip rings. However, these arrangements are difficult to implement.
Non-contact, optical based torque sensors are also known. Such sensors make use of a flexure or shaft, typically formed of metal. One end of the shaft is connected to a driving member, such as a motor, and the other end is connected to a tool or bit which drives a fastener, such as a bolt, to a tightened state, for example. Increased torque on the output end of the shaft as the bolt tightens causes rotation of the output end to lag behind rotation of the driven input end of the shaft. This lag can be used as an indicator of the amount of rotation of the output end which is proportional to the applied torque.
An example of an optically based torsion sensor for measuring torsion in a rotating shaft requires usage of a band consisting of alternating high and low reflectivity regions, The band is stationed on the shaft at the desired location of measurement. One sensor head is located to correspond to each band. Light is projected onto the respective band by the corresponding sensor. Furthermore, each sensor collects the light reflected by the high reflectivity region(s) of the corresponding band. The phase displacement between the intensities of the reflected light at the sensor heads is used to determine torsion on the rotating shaft.
However, it would be desirable to provide a torque sensor with non-contact optics to make implementation a lot simpler than conventional torque measurement methods and devices. It would also be desirable to provide a torque sensor that is not just limited to the measurement of a dynamic torque, but is also capable of measuring torque angle and flexure direction of travel without flexure rotational movement, i.e., in a stall condition.